Brain Rules (notes from John Medina's book)

Exercise gets blood to your brain, bringing it glucose for energy and oxygen to soak up the toxic electrons that are left over. It stimulates the protein that keeps neurons connecting.

Aerobic exercise just twice a week halves your risk of general dementia. It cuts our risk of Alzheimer's by 60 percent.

Rule #2: The human brain evolved (we have three brains)

We don't have one brain in our heads; we have three. We started with a "lizard brain" to keep us breathing, then added a brain like a cat's, and then topped those with the thin layer of Jell-O known as the cortex--the third, and powerful, "human" brain.

We took over the Earth by adapting to change itself, after we were forced from the trees to the savannah when climate swings disrupted our food supply.

Going from four legs to two to walk on the savannah freed up energy to develop a complex brain.

Symbolic reasoning is a uniquely human talent. It may have arisen from our need to understand one another's intensions and motivations, allowing us to coordinate within a group.

Rule #3: Every brain is wired differently

What you do and learm in life physically changes what your brain looks like--it literally rewires it.

The various regions of the brain develop at different rates in different people.

No two people's brains store the same information in the same way in the same place.

We have a great number of ways of being intelligent, many of which don't show up on IQ tests.

Rule #4: People don't pay attention to boring things

The brain's attentional "spotlight" can focus on only one thing at a time: no multitasking.

We are better at seeing patterns and abstracting the meaning of an event than we are at recording detail.

Emotional arousal helps the brain learn.

Audiences check out after 10 minutes, but you can keep grabbing them back by telling narratives or creating events rich in emotion.

Rule #5: Repeat to remember

The brain has many types of memory systems. One type follows for stages of processing: encoding, storing, retrieving, and forgetting.

Information coming into your brain is immediately split into fragments that are sent to different regions of the cortex for storage.

Most of the events that predict whether something learned also will be remembered occur in the first few seconds of learning. The more elaborately we encode a memory during its initial moments, the stronger it will be.

You can improve your chances of remembering soething if you reproduce the environment in which you first put it into your brain.

Rule #6: Remember to repeat

Most memories disappear within minutes, but those that survice the fragile period strengthen with time.

Long-term memories are formed in a two-way conversation between the hippocampus and the cortex, until the hippocampus breaks the connection and the memory is fixed in the cortex--which can take years.

Our brains give us an approximatate view of reality, because they mix new knowledge with past memories and store them together as one.

The way to make long-term memory more reliable is to incorporate new information gradually and repeat it in timed intervals.

Rule #7: Sleep well, think well

The brain is in a constant state of tension between cells and chemicals that try to put you to sleep and cells and chemicals that try to keep you awake.

The neurons of your brain show vigorous rhytmical activity when your're asleep--perhaps replaying what you learned that day.

People vary in how much sleep they need and when they prefer to get it, but the biological drive for an afternoon nap is universdal.

Your body's defense system--the release of adrenaline and cortisol--is built for an immediate response to a serious but passing danger, such as a saber-toothed tiger. Chronic stress, such as hostility at home, dangerously deregulates a system built only to deal with short-term responses.

Under chronic stress, adrenaline creates scars in your blood vessels that can cause a heart attack or stroke, and cortisol damages the cells of the hippocammpus, crippling your ability to learn and remember.

Individually, the worst kind of stress is the feeling that you have no control over the problem--your are helpless.

Emotioanl stress has huge impacts across society, on children's ability to learn in school and on employees' productivity at work.

Rule #9: Stimulate more of the senses at the same time

We absorb information about an event through our senses, translate it into electrical signals, (some for sight, others from sound, etc.), disperse those signals to separate parts of the brain, then reconstruct what happened, eventually perceiving the event as a whole.

The brain seems to rely partly on past experiences in deciding how to combine these signals, so two people can perceive the same event very differently.

Our senses evolved to work together--vision influencing hearing, for example-- which means that we learn best if we stimulate several senses at once.

Smells have an unusual power to bring back memories, maybe because smell signals bypass the thalamus and head straight to their destinations, which include that supervisor of emotions known as the amygdala.

What we see is only what our brain tells us we see, and it's not 100 percent accurate.

The visual analysis we do has many steps. The retina assembles photons into little movie-like streams of information. The visual cortex processes these streams, some areas registering motion, others registering color, etc. Finally, we combine that information back together so we can see.

We learn and remember best through pictures, not through written or spoken words.

Rule #11: Male and female brains are different

The X chromosomes that males have one of and females have two of--though one acts as a backup--is a cognitive "hot spot", carrying an unusually large percentage of genes involved in brain manufacture.

Women are genetically more complex, because the active X chromosomes in their cells are a mix of Mom's and Dad's. Men's chromosomes all come from Mom, and their Y chromosome carries less than 100 genes, compared with about 1,500 for the X chromosome.

Men's and women's brains are different structurally and biochemically--men have a bigger amygdala and produce serotonin faster, for example--but we don't know if those differences have significance.

Men and women respond differently to acute stress: women activate the left hemisphere's amydala and remember the emotional details. men use the right amydgdala and get the gist.

Rule #12: We are powerful and natural explorers

Babies are the model of how we learn--not by passive raction to the environment but by active testing trhrogh observation, hypothesis, experiment, and conclusion.

Specific parts of the brain allow this scientific approach. The right prefrontal cortex looks for errors in our hypothesis ("The saber-toothed tiger is not harmless"), and an adjoining region tells us to change behavior ("Run!").

We can recognize and imitate behavior because of "mirror neurons" scattered across the brain.

Some parts of our adult brains stay as malleable as a baby's, so we can create neurons and learn new things throughout our lives.